Tube heater in engine box

[Refueler]

Looking at Tube Heater to put in the engine box of one of my boats .... with Yanmar 2GM20 raw water cooled

Tubular heaters 1ft 45W 2ft 80W 3ft 135W 4ft 180W 5ft 225W 6ft 270W & Brackets | eBay

Thinking the 135W version ....

I do plan to open the drains on the block as manual says ... last year - I ran A/F through the engine as well ....

 

[GEM43]

You just need one of these now to switch it depending on temperature parameters

 

[Refueler]

Our winters drop to about -25C and lower ... so its really an all-time on job !!

But a Thermostat controlled is worth it ..

 

[NormanS]

I have a 120w tube, hanging beside the engine, fed through a thermostat socket. The engine is fresh water cooled, so there's antifreeze in the engine, but between water traps and 'mufflers' there's an amazing volume of raw water in the exhaust system. To protect it, I use the old antifreeze instead of the raw water immediately before final shut down. I've seen temperatures down to -16°C.

 

[Refueler]

I am wondering if it would be better to have 2 lesser Wattage tubes than a single one ?

Conq 38cr 2GM20 :

Primor 24 VP AQ170 :

The Conq38cr is of course diesel - so very low risk of fire .... but the Primor is a petrol engine - with higher risk if anything goes wrong with heaters ...
Tube heaters are of course enclosed and should be safer than a typical Frost Heater with only a caged element.
I have a number of thermostat 500w frost protection heaters. One actually protects my water cooled Laser Cutter !